1. Field of the Invention
The present invention relates in general to fuel pumps and more particularly to pressure fuel pumps suitable to a fuel injection system of an automotive internal combustion engine. More specifically, the present invention is concerned with pressure fuel pump devices of a type which comprises a pump body having a cam chamber, a cylinder installed in the pump body, a plunger reciprocatively movably disposed in the cylinder to define in the cylinder a pump chamber, a drive shaft projected into the cam chamber, a rotation cam installed in the cam chamber and tightly disposed on the projected portion of the drive shaft to push up the plunger under rotatlon thereof, and a lubricating oil supply system for feeding the cam chamber with a lubricating oil.
2. Description of the Prior Art
For feeding a pressurized fuel to fuel injectors of a fuel injection system of an automotive internal combustion engine, there have been developed pressure fuel pump devices of a type in which a pump proper is arranged above an intake/exhaust valve driving cam shaft of the engine and a plunger of the pump proper is reciprocatively driven by a rotation cam disposed on the cam shaft. In the pressure fuel pump devices of this type, it is inevitably necessary to provide a cylinder head cover with an opening for installing therein the pump proper. This arrangement however tends to induce not only a complicated and bulky construction of the engine but also a limited layout of parts of the engine.
To eliminate these drawbacks, there has been proposed a type in which a drive shaft having the rotation cam mounted thereon is installed in a pump body for reclprocatlvely driving the plunger. In this type, it is necessary to drivingly connect the intake/exhaust valve driving cam shaft to the drive shaft. One of the pressure fuel pump devices of this type is disclosed by Japanese Utility Model First Provisional Publication 4-117185. In the pressure fuel pump device of this publication, there are defined in the pump body cam and bearing chambers at a portion isolated from a pump chamber of the pump proper and the two chambers are filled with a lubricating oil to lubricate various parts and portions installed therein.
However, even the pressure fuel pump device of the publication fails to satisfy users for such a reason that the lubricating ability of the oil may deteriorate in a relatively short time. In fact, the pressure fuel pump device of the publication is so constructed as to shut the lubricating oil in the two chambers, which has a high possibility of hastening deterioration of the lubricating oil.